Tunable Charge Injection via Solution-Processed Reduced Graphene Oxide Electrode for Vertical Schottky Barrier Transistors

We demonstrate, for the first time, the use of a solution-processed reduced graphene oxide (rGO) layer as a work function tunable electrode in vertical Schottky barrier (SB) transistors. The rGO electrodes were deposited by simple spray-coating onto the substrate. The vertical device structure was formed by sandwiching a N,N′-dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C8) organic semiconductor between rGO and Al electrodes. By varying the voltage applied to the gate electrode, the work function of rGO and thus the SB formed at the rGO-PTCDI-C8 interface could be effectively modulated. The resulting vertical SB transistors based on rGO-PTCDI-C8 heterostructures exhibited excellent electrical properties, including a maximum current density of 17.9 mA/cm2 and an on–off current ratio >103, which were comparable with the values obtained for the devices based on a CVD-grown graphene electrode. The charge injection properties of the vertical devices were systematically investigated through temperature-dependent transport measurements. Charge injection was dominated by thermionic emission at high temperature. As the temperature decreased, however, impurity state-assisted hopping occurred. At low temperature and negative gate voltage, the reduced width of barrier induced by a high drain voltage yielded Fowler–Nordheim tunneling at the interface. The use of scalable solution-processed rGO as a work function tunable electrode in vertical SB transistors opens up new opportunities for realizing future large-area flexible two-dimensional materials-based electronic devices.